This style of writing is often extended and in depth. At school and college you would have been asked to tell a story. This probably would have been done in a linear style i.e. starting at the beginning, with a middle and an end.
At university you are expected to focus upon an issue and examine it in detail - not just describe the whole story. Also another important aspect of academic writing is that you are expected to support any opinions you have with evidence. This is where referencing comes in. By reading books, journals, web pages; listening to and watching audio visual materials these can help shape your ideas, support your arguments and discredit the arguments of others.
Take a look at this presentation, note the things you're not already doing and try and put them into practice.
The following texts are all useful for helping you improve your academic writing. You'll find that many of the tips found on the preparing for university pages are echoed in these books.
All three titles are available at the Hive and there may also be copies in other Worcestershire County libraries. Clicking on the title or book cover will take you to the record in the library catalogue.